1. Field
A linear compressor is disclosed herein.
2. Background
Cooling systems are systems in which a refrigerant circulates to generate cool air. In such a cooling system, processes of compressing, condensing, expanding, and evaporating the refrigerant are repeatedly performed. For this, the cooling system includes a compressor, a condenser, an expansion device, and an evaporator. Also, the cooling system may be installed in a refrigerator or air conditioner which is a home appliance.
In general, compressors are machines that receive power from a power generation device, such as an electric motor or a turbine, to compress air, a refrigerant, or various working gases, thereby increasing pressure. Compressors are being widely used in home appliances or industrial fields.
Compressors may be largely classified into reciprocating compressors, in which a compression space into/from which a working gas is suctioned and discharged, is defined between a piston and a cylinder to allow the piston to be linearly reciprocated into the cylinder, thereby compressing a refrigerant, rotary compressors, in which a compression space into/from which a working gas is suctioned or discharged, is defined between a roller that eccentrically rotates and a cylinder to allow the roller to eccentrically rotate along an inner wall of the cylinder, thereby compressing a refrigerant, and scroll compressors, in which a compression space into/from which a refrigerant is suctioned or discharged, is defined between an orbiting scroll and a fixed scroll to compress a refrigerant while the orbiting scroll rotates along the fixed scroll. In recent years, a linear compressor, which is directly connected to a drive motor, in which a piston linearly reciprocates, to improve compression efficiency without mechanical losses due to movement conversion, and having a simple structure, is being widely developed. In general, the linear compressor may suction and compress a refrigerant while a piston linearly reciprocates in a sealed shell by a linear motor and then discharge the refrigerant.
The linear motor is configured to allow a permanent magnet to be disposed between an inner stator and an outer stator. The permanent magnet may linearly reciprocate by an electromagnetic force between the permanent magnet and the inner (or outer) stator. Also, as the permanent magnet operates in the state in which the permanent magnet is connected to the piston, the permanent magnet may suction and compress the refrigerant while linearly reciprocating within the cylinder and then discharge the refrigerant.
The present applicant has filed a patent (hereinafter, referred to as “Prior Art Document 1”) and then has registered the patent with respect to the linear compressor, Korean Patent Registration No. 10-1307688, registered on Sep. 5, 2013 and entitled “LINEAR COMPRESSOR”, which is hereby incorporated by reference. The linear compressor according to the Prior Art Document 1 includes a shell for accommodating a plurality of parts. A vertical height of the shell may be somewhat high as illustrated in FIG. 2 of the Prior Art Document 1. Also, an oil supply assembly for supplying oil between a cylinder and a piston may be disposed within the shell.
When the linear compressor is provided in a refrigerator, the linear compressor may be disposed in a machine room provided at a rear side of the refrigerator. In recent years, a major concern of a customer is increasing an inner storage space of the refrigerator. To increase the inner storage space of the refrigerator, it may be necessary to reduce a volume of the machine room. Also, to reduce the volume of the machine room, it may be important to reduce a size of the linear compressor.
However, as the linear compressor disclosed in the Prior Art Document 1 has a relatively large volume, it is necessary to increase a volume of a machine room into which the linear compressor is accommodated. Thus, the linear compressor having a structure disclosed in the Prior Art Document 1 is not adequate for the refrigerator for increasing the inner storage space thereof.
To reduce the size of the linear compressor, it may be necessary to reduce a size of a main part or component of the compressor. In this case, performance of the compressor may deteriorate. To compensate for the deteriorated performance of the compressor, the compressor drive frequency may be increased. However, the more the drive frequency of the compressor is increased, the more a friction force due to oil circulating into the compressor increases, deteriorating performance of the compressor.
To solve these limitations, the present applicant has filed a patent application (hereinafter, referred to as “Prior Art Document 2”), Korean Patent Publication No. 10-2016-0000324 published on Jan. 4, 2016, and entitled “LINEAR COMPRESSOR”. In the linear compressor of the Prior Art Document 2, a gas bearing technology in which a refrigerant gas is supplied in a space between a cylinder and a piston to perform a bearing function is disclosed.
In the linear compressor according to the Prior Art Document 2, a bearing space between the cylinder and the piston has a small size, to cause causing a limitation in which that an inflow of a refrigerant through a nozzle of the cylinder is not smooth. Thus, the refrigerant may be reduced in pressure, and thus, a lifting force of the piston due to the gas bearing may not be high. As a result, there is a limitation in which that a friction force between the reciprocating piston and the cylinder occurs.
Also, although the refrigerant has to be uniformly introduced over an outer circumferential surface of a piston body, a relatively large amount of gas bearing may be supplied to a position at which the refrigerant pressure is high, that is, a front side of the piston, and thus, the lifting force of the piston may be relatively low at a rear side of the piston. As a result, an unbalance in lifting force may occur between the front and rear sides of the piston, and thus, the gas bearing may be deteriorated in performance.
Also, the refrigerant gas used as the gas bearing may not be discharged to the inside of the shell, but flow to a compression space of the cylinder, and thus, be compressed again, thereby deteriorating the compression performance of the refrigerant.